1. Field of the Invention
The present invention is related to a drive device of a mechanical press. The mechanical press is a two-step speed reduction, one point mechanical press.
2. Description of the Related Art
In a plastic forming process, it is essential that the workpiece is formed at a proper forming speed, so that it is necessary to adjust the downward speed of the slide in accordance with the process. Therefore, a speed reducing mechanism is built into the drive device that drives the slide up and down. The reduction mechanism is normally designed as a single-step reduction of a two-step reduction unit.
Examples of single-step reduction mechanism are disclosed in Unexamined Publication of Patent Application H06-063799 and H11-33797, while examples of two-step reduction mechanism are disclosed in Unexamined Publication of Patent Application H06-155099 and H10-314996. The titles and part numbers used in the following descriptions are according to these publications.
Unexamined Publication of Patent Application H06-063799 shows a mechanical press of one point type with a single connecting rod, having a single-stage reduction mechanism. The drawing shows a flywheel 4 being driven rotationally by means of a motor 2 and a belt 3. A pinion gear 6 is provided on a transmission shaft 5 of flywheel 4 and a main gear 7 is provided on a crankshaft 8, wherein pinion gear 6 meshes with main gear 7. Crankshaft 8 and connecting rod 9 constitute a crank mechanism and a slide 10 is driven up and down by said crank mechanism.
Speed reduction is accomplished by means of said pinion gear 6 and main gear 7. In other words, H06-063799 is a mechanical press with a single-step speed reduction mechanism consisting of pinion gear 6 and main gear 7.
Unexamined Publication of Patent Application H11-33797 also shows a mechanical press of one point type with a single-stage speed reduction mechanism. In FIG. 1, a pinion gear 8 meshes with a main gear 9.
Unexamined Publication of Patent Application H06-155099 shows a mechanical press of two point type with a two-step speed reduction mechanism. In FIG. 2, a gear train 8c constitutes a one-step speed reducing mechanism and addition of a main gear 8b makes it a two-step speed reducing mechanism. A connecting rod 8e engages with an eccentric part 8d provided on main gear 8b thus constituting a so-called “crankless” mechanism. Despite its name of “crankless,” it is essentially a crank mechanism and a slide 7 moves up and down with the help of this crank mechanism.
In the figure of said Unexamined Publication of Patent Application H10-314996, a drive gear 17 and a right intermediate gear 16A constitute a first-step speed reduction mechanism, while a right pinion gear 15A and a right main gear 13A constitute a second-step speed reduction mechanism.
In all of the abovementioned single-step speed reduction or two-step speed reduction mechanisms, a pair of a small gear (pinion gear, etc.) and a large gear (main gear, etc.) are meshing. In all of these speed reduction mechanisms, the main gear tends to be too large, making it difficult to make the entire mechanical press more compact.